Path: utzoo!utgpu!water!watmath!clyde!rutgers!sdcsvax!sdcc6!ix426
From: ix426@sdcc6.ucsd.EDU (tom stockfish)
Newsgroups: comp.lang.c
Subject: Re: Power operator?
Message-ID: <3565@sdcc6.ucsd.EDU>
Date: 7 Jan 88 01:47:22 GMT
References: <47000029@uxe.cso.uiuc.edu>
Reply-To: ix426@sdcc6.ucsd.edu.UUCP (tom stockfish)
Organization: University of California, San Diego
Lines: 53

In article <47000029@uxe.cso.uiuc.edu> mcdonald@uxe.cso.uiuc.edu writes:
>I've been wondering why there is no power operator in C. Did the ANSI 
>committee consider adding one, and if so, why wasn't it done? I'm
>referring to the construct in fortran  X**2  or X**7 . This would seem
>to be extremely useful and trivial to implement.
>
>Doug McDonald

Useful, yes, but fortran syntax (x**y) already means "fetch the value at address
y and multiply by x".  For example,

	double	x =	2;
	double	y =	3;
	double	*z =	&y;
	printf( "%f\n", x**z );

prints "6".  My only complaint about C's operator symbols is that "*" is
grossly overworked.  For example, the following code might look o.k., 
but do you see what's wrong?  In fact, it even compiled (!) with no error
messages or warnings on the Berkeley Unix's cc a few years back (no,
it didn't run properly).

	f( x, y )
		double	*x, *y;
	{
		return	*x/*y;
	}

Of course, Everyone Knows that polynomials should never be calculated as, e.g.
a*x**4 + b*x**3 + c*x**2 + d*x + e (using fortran notation), so that an
exponential operator shouldn't be used here, but there are other important
uses such as (again using fortran)

	f(x) ** 2

where I don't want to call f() twice, and I don't want to clutter up my code 
with temporaries.
	
The syntax x^y is bad because this is already defined for integers as bit-wise
exclusive or.
x^^y is a possibility, altho those who want ^^ for logical
exclusive or will I'm sure complain.
x%%y would probably be o.k., but it looks pretty wierd.
I suppose x!y would work, but I would guess that the
numerical people who want exponentiation as an operator would confuse ! with
factorial.
How about x@y ?
How about x..y ?
How about some better suggestions?

-- 

||  Tom Stockfisch, UCSD Chemistry   tps@chem.ucsd.edu